lib/poset: split `show_dot` in two methods

And escape the strings!

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/lib/poset.nit b/lib/poset.nit
index 7a26f90..9549e48 100644 (file)
--- a/lib/poset.nit
+++ b/lib/poset.nit
@@ -126,28 +126,40 @@ class POSet[E: Object]
                return fe.dtos.has(t)
        end
 
-       # Display the POSet in a gaphical windows.
-       # Graphviz with a working -Txlib is expected.
-       # Used fo debugging.
-       fun show_dot
+       # Write the POSet as a graphviz digraph.
+       #
+       # Nodes are identified with their `to_s`.
+       # Edges are unlabeled.
+       fun write_dot(f: OStream)
        do
-               var f = new OProcess("dot", "-Txlib")
-               #var f = stdout
                f.write "digraph \{\n"
                for x in elements.keys do
-                       f.write "\"{x}\";\n"
+                       var xstr = x.to_s.escape_to_dot
+                       f.write "\"{xstr}\";\n"
                        var xe = self.elements[x]
                        for y in xe.dtos do
+                               var ystr = y.to_s.escape_to_dot
                                if self.has_edge(y,x) then
-                                       f.write "\"{x}\" -> \"{y}\"[dir=both];\n"
+                                       f.write "\"{xstr}\" -> \"{ystr}\"[dir=both];\n"
                                else
-                                       f.write "\"{x}\" -> \"{y}\";\n"
+                                       f.write "\"{xstr}\" -> \"{ystr}\";\n"
                                end
                        end
                end
                f.write "\}\n"
-               #f.close
-               #f.wait
+       end
+
+       # Display the POSet in a graphical windows.
+       # Graphviz with a working -Txlib is expected.
+       #
+       # See `write_dot` for details.
+       fun show_dot
+       do
+               var f = new OProcess("dot", "-Txlib")
+               f.write "\}\n"
+               write_dot(f)
+               f.close
+               f.wait
        end
 
        # Compare two elements in an arbitrary total order.